title: Evolutionarily stable attenuation by genome rearrangement in a virus.
abstract: Live, attenuated viruses provide many of the most effective vaccines. For the better part of a century, the standard method of attenuation has been viral growth in novel environments, whereby the virus adapts to the new environment but incurs a reduced ability to grow in the original host. The downsides of this approach were that it produced haphazard results, and even when it achieved sufficient attenuation for vaccine production, the attenuated virus was prone to evolve back to high virulence. Using bacteriophage T7, we apply a synthetic biology approach for creating attenuated genomes and specifically study their evolutionary stability. Three different genome rearrangements are used, and although some initial fitness recovery occurs, all exhibit greatly impaired abilities to recover wild-type fitness over a hundred or more generations. Different degrees of stable attenuation appear to be attainable by different rearrangements. Efforts to predict fitness recovery using the extensive background of T7 genetics and biochemistry were only sometimes successful. The use of genome rearrangement thus offers a practical mechanism of evolutionary stable viral attenuation, with some progress toward prediction.
authors.affiliation: Department of Integrative Biology, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Nicole
authors.initials: N
authors.lastname: Cecchini
authors.forename: Matthew
authors.initials: M
authors.lastname: Schmerer
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Molineux
authors.forename: Rachael
authors.initials: R
authors.lastname: Springman
authors.forename: James J
authors.initials: JJ
authors.lastname: Bull
mesh_terms: D017123:Bacteriophage T7 / Q000235:genetics*; D005075:Biological Evolution; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D015321:Gene Rearrangement; D016679:Genome, Viral; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism; D014774:Virulence / Q000235:genetics
chemical_list: D014764:Viral Proteins; D012321:DNA-Directed RNA Polymerases
keywords: adaptation; attenuation; engineering; genome; synthetic biology; virus